Preparation method and application of nano-biomass oilfield water plugging agent

Abstract

The present invention discloses a preparation method and application of a nano-biomass oilfield water plugging agent, and belongs to the technical field of oil extraction industry. The present invention first prepares a prefabricated liquid by polymerizing acrylamide and utilizing the effect of chemical cross-linking with biomass components, and then transports the prefabricated liquid to the area requiring plugging for in-situ molding to obtain the nano-biomass oilfield water plugging agent. The nano-biomass oilfield water plugging agent prepared by the present invention has good high temperature resistance and excellent adhesion performance. As an oilfield water plugging agent, it has the advantages of high strength, good adhesion, high temperature resistance, good plugging effect, and easy degradation. At the same time, the preparation method of the present invention has mild technical conditions and is easy to operate, which can greatly improve production efficiency and respond to water plugging needs more quickly, thereby reducing operation time and cost.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a nano-biomass oilfield water plugging agent, belonging to the technical field of oil mining industry. Background Art

[0002] In most mature oilfield systems in the world, excessive water production is one of the most concerning issues. Water recovery greatly increases the cost of oil production, and also brings a series of problems such as corrosion of oil production equipment, sand production in oil wells, and oil layer collapse. Necessary water plugging is the key to solving this problem. Among the common methods of water plugging, chemical water plugging is widely used. Many oilfields usually use some chemical plugging agents to plug the water layer, and inject polymers or tiny particles to plug a large number of irregular pipeline spaces, thereby improving the oil recovery rate.

[0003] In practical applications in recent years, the most widely used oilfield water plugging agent is the high molecular weight polymer polyacrylamide. For example: Patent CN202111281840.6 discloses a raw material composition of a high temperature and high salt resistant plugging agent, which includes a salt-resistant acrylamide polymer, a cross-linking agent, a deoxidizer and an enhancer. The main raw material used is a high molecular weight polymer polyacrylamide with a viscosity-average molecular weight of 6 million to 15 million, and the raw material does not contain biomass components, which makes it impossible to degrade and will remain underground for a long time; in addition, the cross-linking agents used in this patent are extremely unfriendly to the environment, and therefore will greatly pollute the environment. Due to the large amount of oilfield water plugging agents used, if too much difficult-to-degrade or environmentally unfriendly materials are used, it will pose a threat to the formation and operators, which is not conducive to sustainable development. Therefore, the development of biopolymer-based, degradable chemical plugging agents is of great practical significance.

[0004] Cellulose material is the most abundant renewable biomass resource on land and is widely found in various types of plant fiber raw materials. Nanocellulose, as a biomass nanopolysaccharide material with good performance and wide application, has shown great potential in extreme environment gel materials, thermosetting elastomer materials, 3D printing materials, nanocomposites and other fields, and has aroused the research interest of many scholars.

[0005] As a polysaccharide formed by the fermentation of the fungus Sclerotium, scleroglucan can also be used as a component of gel material. There are also a large number of hydroxyl groups on the scleroglucan molecular chain, which has good modification and cross-linking advantages. Related studies have shown that scleroglucan has a rod-shaped rigid triple helical molecular structure, so it has excellent thermal stability and salt resistance, and can be stable in a wide pH range.

[0006] At present, some studies have applied polysaccharide gels to the field of oilfield plugging. For example, patent CN202211577665.X proposes a method for preparing a temporary plugging agent composed of acrylamide and biodegradable fibers. However, its preparation process is complicated and requires the addition of hydroxides to graft biodegradable fibers into high molecular polymers. The amount of N,N-methylenebisacrylamide is large. Moreover, the temporary plugging agent prepared by this method also has problems such as poor high temperature resistance and poor adhesion to the core. Summary of the invention

[0007] In view of the problems that most oilfield water plugging agents have complex preparation processes, poor performance at high temperatures, and inability to degrade, the present invention provides a preparation method and application of a nano-biomass oilfield water plugging agent. The present invention first mixes acrylamide with a biomass component, adds potassium persulfate and a cross-linking agent to prepare a preformed liquid, and then transports the preformed liquid to the area that needs to be plugged for in-situ molding to obtain a nano-biomass oilfield water plugging agent. The nano-biomass oilfield water plugging agent prepared by the present invention has good high temperature resistance and excellent adhesion performance, and as an oilfield water plugging agent, it has the advantages of being able to be in-situ molded, easy to degrade, mild conditions, strong operability, and high production efficiency.

[0008] The first object of the present invention is to provide a method for preparing a prefabricated liquid of a nano-biomass oilfield water plugging agent, comprising the following steps:

[0009] (1) dissolving acrylamide in water, stirring, adding biomass components, stirring and dispersing, and obtaining a mixed solution;

[0010] (2) adding potassium persulfate and a cross-linking agent into the mixed solution, stirring, and obtaining a prefabricated solution of a nano-biomass oilfield water plugging agent.

[0011] In one embodiment, the mass ratio of acrylamide to the biomass component in step (1) is 1:9-9:1, preferably 1:1.

[0012] In one embodiment, the stirring in step (1) is carried out at 100-500 rpm and 15-40° C. for 10-90 min.

[0013] In one embodiment, the biomass component in step (1) is any one of nanocellulose, scleroglucan, guar gum, and nanochitin, or a combination of two or more thereof, preferably a combination of nanocellulose and scleroglucan.

[0014] In one embodiment, the biomass component in step (1) is a combination of nanocellulose and scleroglucan, and the mass ratio of the two is 7:3-3:7, preferably 1:1.

[0015] In one embodiment, the stirring and dispersing in step (1) is carried out at 100-500 rpm and 15-40° C. for 10-90 min, preferably 30 min.

[0016] In one embodiment, the acrylamide and biomass components in the mixed solution of step (1) account for 0.1-5% of the total mass of the mixed solution.

[0017] In one embodiment, the amount of potassium persulfate used in step (2) is 1-10% of the mass of acrylamide, preferably 7%.

[0018] In one embodiment, the cross-linking agent in step (2) is any one of N,N-dimethylbisacrylamide, glutaraldehyde, polyethylene glycol diglycidyl ether, and epichlorohydrin, preferably N,N-dimethylbisacrylamide.

[0019] In one embodiment, the amount of the cross-linking agent added in step (2) is 1-10% by weight of the biomass component, preferably 5%.

[0020] In one embodiment, the stirring in step (2) is carried out at 100-500 rpm and 15-40° C. for 2-4 hours.

[0021] The second object of the present invention is to provide a nano-biomass oilfield water plugging agent prefabricated liquid, which is prepared by the above-mentioned method.

[0022] The third object of the present invention is to provide a method for preparing a nano-biomass oilfield water plugging agent, comprising the following steps:

[0023] The nano-biomass oilfield water plugging agent preformed liquid is pumped to a target area with a temperature of 70-200°C within 0-24 hours after preparation, and the nano-biomass oilfield water plugging agent preformed liquid is allowed to stay for 30 minutes to 8 hours, so that the nano-biomass oilfield water plugging agent can be formed in situ.

[0024] The fourth object of the present invention is to provide a nano-biomass oilfield water plugging agent prepared by the above method.

[0025] The fifth object of the present invention is to provide the use of the above-mentioned nano-biomass oilfield water plugging agent prefabricated liquid or nano-biomass oilfield water plugging agent in oil production.

[0026] Beneficial effects of the present invention:

[0027] (1) The present invention uses acrylamide self-polymerization and cross-linking with biomass components to prepare oilfield water plugging agents, without the need for additional chemical reactions; the molecular weight of the self-polymerized polyacrylamide is small, so it is easy to degrade, reducing the adverse impact on the environment. The water plugging agent prepared by the present invention is more easily decomposed by nature than traditional water plugging agents, effectively reducing the long-term impact on the ecosystem, and providing a more sustainable option for oilfield development.

[0028] (2) The nano-biomass oilfield water plugging agent prepared by the present invention has high strength, good adhesion and good plugging effect. At the same time, the preparation method of the present invention has mild technical conditions and is easy to operate, which can greatly improve production efficiency and respond to water plugging needs more quickly, thereby reducing operation time and cost.

[0029] (3) The nano-biomass oilfield water plugging agent provided by the present invention can remain stable under high temperature conditions, and can withstand a temperature range of 0°C-150°C. It can stably exist in a mass concentration of 1% NaCl, 2% KCl, 1% CaCl 2 and 1% MgCl 2 Its high temperature resistance enables it to maintain excellent performance in extreme working environments, providing a more reliable solution for oilfield operations.

[0030] (4) The in-situ forming characteristics of the nano-biomass oilfield water plugging agent provided by the present invention enable oilfield operators to directly apply it in the required area, and its excellent adhesion performance ensures firm adhesion under unstable geological conditions, greatly improving the application efficiency of the water plugging agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 This is a scanning electron microscope photo of the nano-biomass oilfield water plugging agent prepared in Example 6;

[0033] Figure 2 is a scanning electron microscope photograph of the nano-biomass oilfield water plugging agent prepared in Example 7;

[0034] Figure 3 This is a photo of a sample of the nano-biomass oilfield water plugging agent prepared in Example 8;

[0035] Figure 4 This is a photo of a sample of the nano-biomass oilfield water plugging agent prepared in Example 9;

[0036] Figure 5 The nano-biomass oilfield water plugging agent solid CP-MAS prepared in Example 3 and Example 10 13 C NMR spectrum analysis spectrum, where a is the spectrum with a chemical shift of 60-120 ppm, and b is the spectrum with a chemical shift of 0-200 ppm;

[0037] Figure 6 This is a sample photo of the nano-biomass oilfield water plugging agent prepared in Example 10 after being subjected to a high-temperature water plugging test. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings, technical process steps, specific implementation conditions and materials in the embodiments of the present invention to clearly and completely describe the technical solutions in the examples of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Test method:

[0040] 1. Blockage breakthrough pressure test:

[0041] The sealing performance test used a steel core (Φ2.5 mm × 50 mm) to study the sealing efficiency of the nano-biomass oilfield water plugging agent in the sealing crack. The steel core was used to simulate the formation of a crack with a width of 1 mm.

[0042] The prepared nano-biomass oilfield water plugging agent prefabricated liquid is injected into the cracks and completely gelled in a closed container at 70° C. to form the nano-biomass oilfield water plugging agent.

[0043] The standard experimental procedures are outlined below:

[0044] (1) Assemble all equipment and use saturated saline to verify the leak-proofness of the hydrogel;

[0045] (2) positioning the core containing the nano-biomass oilfield water plugging agent in the support and applying an annular pressure;

[0046] (3) Apply hydraulic pressure through a pump, loading in stages in increments of 0.01 MPa, with each stage lasting 8 minutes;

[0047] Fluid loss and pressure drop were monitored at each stage, and the pressure point at which fluid loss initially occurred was recorded as the breakthrough pressure.

[0048] 2. Rheological test:

[0049] Rheological properties reflect the deformation and flow behavior of a substance under external forces. Hydrogel is a gel with a highly cross-linked structure, and its strength is closely related to the stability and interaction of its internal structure. The rheological properties of the nano-biomass oilfield water plugging agent were tested using a rotational rheometer (DHR-1, USA) with an angular frequency of 0.1-100 rad / s and a test temperature of 25°C.

[0050] The storage modulus of the hydrogel was characterized in detail by rheometer. The storage modulus provides important information about its mechanical properties in describing the strength of the hydrogel. It reflects the elasticity of the material under external loading and can be used to evaluate the internal structure of the hydrogel, the degree of cross-linking, and its behavior under stress.

[0051] 3. High temperature resistance test:

[0052] The high temperature aging performance of the nano-biomass oilfield water plugging agent was tested using a high-pressure reactor. 1% NaCl, 2% KCl, 1% CaCl 2 and 1% MgCl 2 The hydrogel was then placed in a reactor and subjected to a high temperature aging durability test at 140°C. The gel was taken out at regular intervals to observe its integrity.

[0053] 4. Chemical structure test:

[0054] Solid-state CP-MAS 13 C NMR spectroscopy: After freeze-drying, the solid-state structure of the composite hydrogel was characterized using CP-MAS NMR spectroscopy (Burker 400M).

[0055] For each sample, 10,000 scans were collected using a spinning frequency of 10 kHz, a contact time of 4 ms and a delay between pulses of 4 s.

[0056] 5. Degradability test:

[0057] The hydrogel samples to be tested were divided into equal amounts according to their mass and numbered. The prepared samples were then placed in a 50 mL solution containing 1% NaCl, 2% KCl, 1% CaCl 2 and 1% MgCl 2 The sample was completely immersed in a container, and then the container was placed in a constant temperature oven to maintain a high temperature of 150°C. During the test, the changes in the sample were continuously observed, and the mass of the sample was recorded at regular intervals. When the hydrogel was completely destroyed and disappeared, the degradation was completed, and the time when the degradation was completed was recorded.

[0058] The raw materials used in the embodiment:

[0059] The raw material of the nanocellulose used in the present invention can be derived from wood, grass, bamboo, hemp, cotton, etc. In the following examples, the present invention is described using nanocellulose derived from wood as the raw material.

[0060] Nanocellulose: purchased from Tianjin Wood Elf Biotechnology Co., Ltd., the nanocellulose was Tempo-oxidized, with a carboxyl content of 2.46 mmol / L and a diameter of 10-100 nm;

[0061] Scleroglucan: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. (CAS No.: 39464-87-4, mPa.s>2000);

[0062] Acrylamide: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. (CAS No.: 79-06-1, AR, 99.0%);

[0063] Nanofibers: purchased from Tianjin Wood Elf Biotechnology Co., Ltd. (nanofibers containing lignin, with a fiber diameter of 10-100 nm);

[0064] Carboxymethyl cellulose: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. (CAS No.: 9004-32-4, 1500-3100 mPa.s);

[0065] Potassium persulfate: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. (CAS No.: 7727-21-1, AR, 99.5%);

[0066] N,N-dimethylbisacrylamide: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. (CAS No.: 110-26-9, 99%).

[0067] Example 1

[0068] A method for preparing a nano-biomass oilfield water plugging agent comprises the following steps:

[0069] Take 5g of acrylamide and dissolve it in 2000g of water, and stir it at 300rpm and 25℃ for 30min; then take 2.5g of absolute dry mass of nanocellulose and 2.5g of absolute dry mass of scleroglucan, add them to a beaker, and stir and disperse them at 300rpm and 25℃ for 30min to obtain a mixed solution; add 0.35g of potassium persulfate and 0.25g of N,N-dimethylbisacrylamide, and stir at 300rpm and 25℃ for 30min to obtain a nano-biomass oilfield water plugging agent prefabricated liquid;

[0070] The nano-biomass oilfield water plugging agent prefabricated liquid is transported to the target area, and reacted for 4 hours in an environment of 70° C. to obtain the nano-biomass oilfield water plugging agent by in-situ molding.

[0071] The prepared nano-biomass oilfield water plugging agent can maintain good gel morphology and plugging performance at 140°C and in the salt solution environment of the oilfield mineralized layer.

[0072] Example 2

[0073] The difference from Example 1 is that 5 g of acrylamide is dissolved in 1000 g of water and stirred at 300 rpm and 25° C. for 30 min; then 2.5 g of the absolute dry mass of nanocellulose and 2.5 g of the absolute dry mass of scleroglucan are added to a beaker, and stirred and dispersed at 300 rpm and 25° C. for 30 min to obtain a mixed solution. The other conditions and parameters are the same as those in Example 1, and a nano-biomass oilfield water plugging agent is prepared.

[0074] The prepared nano-biomass oilfield water plugging agent can maintain good gel morphology and plugging performance at 140°C and in the salt solution environment of the oilfield mineralized layer.

[0075] Example 3

[0076] The difference from Example 1 is that 5 g of acrylamide is dissolved in 500 g of water and stirred at 300 rpm and 25° C. for 30 min; then 2.5 g of the absolute dry mass of nanocellulose and 2.5 g of the absolute dry mass of scleroglucan are added to a beaker, and stirred and dispersed at 300 rpm and 25° C. for 30 min to obtain a mixed solution. The other conditions and parameters are the same as those in Example 1, and a nano-biomass oilfield water plugging agent is prepared.

[0077] The prepared nano-biomass oilfield water plugging agent can maintain good gel morphology and plugging performance at 140°C and in the salt solution environment of the oilfield mineralized layer.

[0078] Example 4

[0079] The difference from Example 1 is that 5 g of acrylamide is dissolved in 333 g of water and stirred at 300 rpm and 25° C. for 30 min; then 2.5 g of the absolute dry mass of nanocellulose and 2.5 g of the absolute dry mass of scleroglucan are added to a beaker, and stirred and dispersed at 300 rpm and 25° C. for 30 min to obtain a mixed solution. The other conditions and parameters are the same as those in Example 1, and a nano-biomass oilfield water plugging agent is prepared.

[0080] The prepared nano-biomass oilfield water plugging agent can maintain good gel morphology and plugging performance at 140°C and in the salt solution environment of the oilfield mineralized layer.

[0081] Example 5

[0082] The difference from Example 1 is that 5 g of acrylamide is dissolved in 250 g of water and stirred at 300 rpm and 25° C. for 30 min; then 2.5 g of the absolute dry mass of nanocellulose and 2.5 g of the absolute dry mass of scleroglucan are added to a beaker, and stirred and dispersed at 300 rpm and 25° C. for 30 min to obtain a mixed solution. The other conditions and parameters are the same as those in Example 1, and a nano-biomass oilfield water plugging agent is prepared.

[0083] The prepared nano-biomass oilfield water plugging agent can maintain good gel morphology and plugging performance at 140°C and in the salt solution environment of the oilfield mineralized layer.

[0084] Example 6

[0085] The difference from Example 1 is that 5 g of acrylamide is dissolved in 200 g of water and stirred at 300 rpm and 25° C. for 30 min; then 2.5 g of the absolute dry mass of nanocellulose and 2.5 g of the absolute dry mass of scleroglucan are added to a beaker, and stirred and dispersed at 300 rpm and 25° C. for 30 min to obtain a mixed solution. The other conditions and parameters are the same as those in Example 1, and a nano-biomass oilfield water plugging agent is prepared.

[0086] The prepared nano-biomass oilfield water plugging agent can maintain good gel morphology and plugging performance at 140°C and in the salt solution environment of the oilfield mineralized layer.

[0087] Figure 1 This is the microscopic morphology of the nano-biomass oilfield water plugging agent prepared in Example 6. It can be seen from the figure that the prepared material has a typical gel network structure.

[0088] Example 7

[0089] The difference from Example 3 is that 6 g of acrylamide is dissolved in 500 g of water and stirred at 300 rpm and 25° C. for 30 min; then 2 g of the absolute dry mass of nanocellulose and 2 g of the absolute dry mass of scleroglucan are added to a beaker and stirred and dispersed at 300 rpm and 25° C. for 30 min to obtain a mixed solution; 0.42 g of potassium persulfate and 0.2 g of N,N-dimethylbisacrylamide are added;

[0090] Other conditions and parameters are the same as those in Example 1. The prepared nano-biomass oilfield water plugging agent can maintain good gel morphology and plugging performance at 130° C. and in the salt solution environment of the oilfield mineralized layer.

[0091] Figure 2 This is the microscopic morphology of the nano-biomass oilfield water plugging agent prepared in Example 7. It can be seen from the figure that the prepared nano-biomass oilfield water plugging agent has a typical gel network structure.

[0092] Example 8

[0093] The difference from Example 3 is that 7 g of acrylamide is dissolved in 500 g of water and stirred at 300 rpm and 25° C. for 30 min; then 1.5 g of the absolute dry mass of nanocellulose and 1.5 g of the absolute dry mass of scleroglucan are added to a beaker and stirred and dispersed at 300 rpm and 25° C. for 30 min to obtain a mixed solution; 0.49 g of potassium persulfate and 0.15 g of N,N-dimethylbisacrylamide are added;

[0094] Other conditions and parameters are the same as those in Example 1. The prepared nano-biomass oilfield water plugging agent can maintain good gel morphology and plugging performance at 130° C. and in the salt solution environment of the oilfield mineralized layer.

[0095] Figure 3 This is the nano-biomass oilfield water plugging agent prepared in Example 8, wherein the red dotted line represents the horizontal plane of the nano-biomass oilfield water plugging agent. It can be seen from the figure that the hydrogel has a good gelling effect and exhibits solid characteristics.

[0096] Example 9

[0097] The difference from Example 3 is that 8 g of acrylamide is dissolved in 500 g of water and stirred at 300 rpm and 25° C. for 30 min; then 1 g of the absolute dry mass of nanocellulose and 1 g of the absolute dry mass of scleroglucan are added to a beaker and stirred and dispersed at 300 rpm and 25° C. for 30 min to obtain a mixed solution; 0.56 g of potassium persulfate and 0.1 g of N,N-dimethylbisacrylamide are added;

[0098] Other conditions and parameters are the same as those in Example 1. The prepared nano-biomass oilfield water plugging agent can maintain good gel morphology and plugging performance at 120° C. and in the salt solution environment of the oilfield mineralized layer.

[0099] Figure 4 This is the nano-biomass oilfield water plugging agent prepared in Example 9, wherein the red dotted line represents the horizontal plane of the nano-biomass oilfield water plugging agent. It can be seen from the figure that the hydrogel has a good gelling effect and exhibits solid characteristics, and has the same gelling effect as Example 8.

[0100] Example 10

[0101] The difference from Example 3 is that 9 g of acrylamide is dissolved in 500 g of water and stirred at 300 rpm and 25° C. for 30 min; then 0.5 g of the absolute dry mass of nanocellulose and 0.5 g of the absolute dry mass of scleroglucan are added to a beaker and stirred and dispersed at 300 rpm and 25° C. for 30 min to obtain a mixed solution; 0.63 g of potassium persulfate and 0.05 g of N,N-dimethylbisacrylamide are added;

[0102] Other conditions and parameters are the same as those in Example 1. The prepared nano-biomass oilfield water plugging agent can maintain good gel morphology and plugging performance at 120° C. and in the salt solution environment of the oilfield mineralized layer.

[0103] Figure 5 Solid CP-MAS of the nano-biomass oilfield water plugging agent prepared in Example 3 and Example 10 13 The test results of C nuclear magnetic resonance spectroscopy analysis are as follows: a is the spectrum with a chemical shift of 60-120 ppm, and b is the spectrum with a chemical shift of 0-200 ppm; as can be seen from b, the peak at 180 ppm corresponds to C=O, corresponding to C=O in N,N-dimethylbisacrylamide and polyacrylamide, while the carbon signals of nanocellulose and scleroglucan show overlapping signals in the range of 60-110 ppm. This conclusion indicates the successful construction of the composite hydrogel.

[0104] Figure 6 This is a photo of the nano-biomass oilfield water plugging agent prepared in Example 10 after aging for 7 days in a high temperature environment of a simulated oilfield mineralized layer. It can be seen that the material in the photo still has a typical gel-like structure.

[0105] Embodiment 11

[0106] The difference from Example 3 is that 0.15 g of potassium persulfate (equivalent to 3% of the mass of acrylamide) and 0.35 g of N,N-dimethylbisacrylamide (equivalent to 7% of the total mass of nanocellulose and scleroglucan) are added, and the nano-biomass oilfield water plugging agent preform is transported to the target area and reacted for 3 hours at 70°C to obtain the nano-biomass oilfield water plugging agent by in-situ molding.

[0107] The prepared nano-biomass oilfield water plugging agent can maintain good gel morphology and plugging performance at 140°C and in the salt solution environment of the oilfield mineralized layer.

[0108] Example 12

[0109] The difference from Example 3 is that 0.15 g of potassium persulfate (equivalent to 3% of the mass of acrylamide) and 0.5 g of N,N-dimethylbisacrylamide (equivalent to 10% of the total mass of nanocellulose and scleroglucan) are added, the nano-biomass oilfield water plugging agent preform is transported to the target area, and the nano-biomass oilfield water plugging agent is obtained by in-situ molding by reacting for 30 minutes at 70°C.

[0110] The prepared nano-biomass oilfield water plugging agent can maintain good gel morphology and plugging performance at 140°C and in the salt solution environment of the oilfield mineralized layer.

[0111] Embodiment 13

[0112] The difference from Example 3 is that 0.5 g of potassium persulfate (equivalent to 10% of the mass of acrylamide) and 0.05 g of N,N-dimethylbisacrylamide (equivalent to 1% of the total mass of nanocellulose and scleroglucan) are added, and the nano-biomass oilfield water plugging agent preform is transported to the target area and reacted for 8 h at 70° C. to obtain the nano-biomass oilfield water plugging agent by in-situ molding.

[0113] The prepared nano-biomass oilfield water plugging agent can maintain good gel morphology and plugging performance at 140°C and in the salt solution environment of the oilfield mineralized layer.

[0114] Comparative Example 1: Nanocellulose is replaced by carboxymethyl cellulose

[0115] The difference from Example 3 is that the nanocellulose is replaced by carboxymethyl cellulose, and the other conditions and parameters are the same as those of Example 3.

[0116] Comparative Example 2: Nanocellulose is replaced by nanofiber

[0117] The difference from Example 3 is that nanocellulose is replaced by nanofibers, and other conditions and parameters are the same as those of Example 3.

[0118] Comparative Example 3 only uses nanocellulose

[0119] The difference from Example 3 is that no scleroglucan is added, and only nanocellulose is used. The mass of the nanocellulose is 5 g. Other conditions and parameters are the same as those in Example 3.

[0120] Comparative Example 4 only uses scleroglucan

[0121] The difference from Example 3 is that no nanocellulose is added, and only scleroglucan is used. The mass of scleroglucan is 5 g. Other conditions and parameters are the same as those in Example 3.

[0122] Comparative Example 5 does not use in-situ molding

[0123] The nano-biomass oilfield water plugging agent preform prepared in Example 3 was subjected to a reaction condition of 70° C. for 4 hours under a ground environment. It was difficult to pump the polymerized gel to the specified position of the detection instrument without using an in-situ molding method, so the plugging breakthrough pressure could not be detected.

[0124] Comparative Example 6: Preparation of water plugging agent using high molecular weight acrylamide polymer

[0125] 10 g of polyacrylamide with a molecular weight of 8-15 million was added to 1000 mL of water, and stirred at 300 rpm and 80° C. for 60 min. 0.2 g of glutaraldehyde as a cross-linking agent and 0.3 g of % thiourea as a deoxidizer were added, and stirred at 600 rpm and 25° C. for 30 min to obtain a high molecular weight polyacrylamide water plugging agent prefabricated liquid.

[0126] The high molecular weight polyacrylamide water plugging agent prefabricated liquid is transported to the target area, and reacted for 4 hours in an environment of 70° C. to obtain the high molecular weight polyacrylamide water plugging agent by in-situ molding.

[0127] The performance of the water plugging agents of Examples 1-13 and Comparative Examples 1-6 was tested, and the test results are as follows:

[0128] Table 1

[0129]

[0130] Note: “ / ” indicates that the performance cannot be measured

[0131] From Table 1, we can see that:

[0132] (1) As the proportion of acrylamide and biomass components in the total mass of the mixed solution increases, the plugging effect of the gel (the higher the plugging breakthrough pressure), reaches the best at 2%.

[0133] (2) When the proportion of acrylamide reaches 50%, the blocking effect is best.

[0134] (3) Potassium persulfate (KPS) affects the polymerization degree of acrylamide, while the addition amount of N,N-methylenebisacrylamide affects the degree of cross-linking between biomass components, and the two act synergistically.

[0135] (4) Replacing nanocellulose with carboxymethyl cellulose or other nanofibers will significantly reduce the performance of the gel (including anti-aging properties and high temperature resistance).

[0136] (5) It is difficult to pump the polymerized gel to the specified position of the detection instrument without using the in-situ molding method, so its blocking effect cannot be detected.

[0137] (6) In the absence of light radiation and other chemical means, high molecular weight polyacrylamide cannot be degraded in this solution environment.

[0138] (7) The temperature of the oil well is related to the well depth. The deeper the well is, the higher the temperature is. Generally, the temperature of a well with a depth of 2000-3000 meters is about 60-80°C. Therefore, the nano-biomass oilfield water plugging agent of the present invention meets the needs of most oil well operations.

[0139] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a prefabricated liquid of a nano-biomass oilfield water plugging agent, characterized in that: The following steps are involved: (1) dissolving acrylamide in water, stirring, adding a biomass component, stirring and dispersing, and obtaining a mixed solution; wherein the biomass component is a combination of nanocellulose and scleroglucan, and the mass ratio of the two is 7:3-3:7; (2) adding potassium persulfate and a cross-linking agent into the mixed solution, stirring, and obtaining a prefabricated solution of a nano-biomass oilfield water plugging agent.

2. The method according to claim 1, characterized in that The mass ratio of acrylamide to biomass component in step (1) is 1:9-9:

1.

3. The method according to claim 1, characterized in that The acrylamide and biomass components described in step (1) account for 0.1-5% of the total mass of the mixed solution.

4. The method according to claim 1, characterized in that: The amount of potassium persulfate used in step (2) is 1-10% of the mass of acrylamide.

5. A nano-biomass oilfield water plugging agent prefabricated liquid, characterized in that: The method is prepared by any one of claims 1 to 4.

6. A method for preparing a nano-biomass oilfield water plugging agent, characterized in that: The steps include: The nano-biomass oilfield water plugging agent preformed liquid of claim 5 is pumped to a target area with a temperature of 70-200°C within 0-24 hours after preparation, and the nano-biomass oilfield water plugging agent preformed liquid is allowed to stay for 30 minutes to 8 hours, so that the nano-biomass oilfield water plugging agent can be formed in situ.

7. A nano-biomass oilfield water plugging agent, characterized in that: The method according to claim 6 is used to prepare the product.

8. Use of the nano-biomass oilfield water plugging agent prefabricated liquid according to claim 5 or the nano-biomass oilfield water plugging agent according to claim 7 in oil production.

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